Abstract

Background: Despite many preclinical studies showing the anti-neoplastic effects of vitamin D on breast cancer, findings from epidemiologic studies and randomized trials remain inconclusive. It is possible that tumor heterogeneity in breast cancer may mask these associations. Variations in vitamin D metabolism may explain some racial disparities in breast cancer. We aimed to examine the association of serum vitamin D levels with individual patient and tumor characteristics.

Results: Among the 200 breast cancer patients identified, the mean age was 55.9 years (range 29-90). Ethnicities of the patients were as follows: 104 (52%) Caucasian, 43 (22%) African American, 29 (15%) Hispanic, and 16 (8%) Asian. Seventy six patients (38%) were premenopausal, and 124 (62%) were postmenopausal. African Americans were found to have higher rates of triple negative tumors compared to all other ethnicities (24.4% vs. 11.6%, p = 0.029). Younger women had lower mean serum 25(OH)D levels compared to older women (p = 0.033). Lower mean 25(OH)D levels were seen in ER negative tumors compared to ER positive tumors (p = 0.0102). Mean 25(OH)D levels were lower in African American, Hispanic, and Asian breast cancer patients when compared to Caucasians (p = 0.0004). When stratifying by menopausal status, serum 25(OH)D levels differed more by tumor characteristics among premenopausal women than postmenopausal women. In premenopausal women, lower vitamin D levels were seen in patients who were African Americans (p = 0.0185), and with tumors that were ER negative (p = 0.0083). There was also a trend toward lower mean vitamin D levels in those with TN breast cancer compared to other molecular subtypes.

Conclusion: In premenopausal women, lower vitamin D levels were associated with African American race, younger age, and ER negative tumors. This may suggest that African Americans have defective vitamin D metabolism that may contribute to a more aggressive breast cancer phenotype. Further studies are warranted.